Variable inductor having core saturation controlled by magnet



' R. PIETERS Dec. 19, 1967 VARIABLE INDUCTOR HAVING CORE SATURATION CONTROLLED BY MAGNET Filed Aug. 10, 1965 FIG] INVENTOR RICHARD PIETERS AGENT United States Patent 3,359,519 VARIABLE INDUCTOR HAVING CORE SATURA- TION CONTROLLED BY MAGNET Richard Pieters, Emmasingel, Eindhoven, Netherlands, as-

signor to North American Philips Company, Inc., New York, N .Y., a corporation of Delaware Filed Aug. 10, 1965, Ser. No. 478,590 Claims priority, application Netherlands, Aug. 11, 1964, 64-2206 6 Claims. (Cl. 336110) This invention relates to coil systems having a satura'ole core, more particularly to linearity correctors for television comprising at least one cylindrical, diametrically-magnetized rotary magnet which engages, at least substantially, one end of the saturable core, which end projects from the winding of the coil and is parallel to the axis of rotation of the magnet. By means of such a device it is possible to obtain a comparatively strong saturation of the coil. In addition, the degree of saturation is readily adjustable by rotating the cylindrical magnet. An object of the invention is to provide a device which permits of obtaining a maximum saturation which is considerably greater than the prior art devices,--while retaining the feature that the degree of saturation is readily adjustable.

The invention is characterized in that the said end of the core of the coil is surrounded in part by a U-shaped permanent magnet, the poles of which lie on the inner side and the outer side of the U respectively, and positioned so that the open side of the U is adjacent the cylindrical magnet.

In order that the invention may be readily carried into effect, it will now be described, in detail, by way of example, with reference to the accompanying diagrammatic drawing, in which:

FIGURE 1 is a and FIGURES 2 and 3 show the device of FIGURE 1 in horizontal section in two adjusted positions.

The coil system shown comprises a winding 1 and a rod-shaped ferromagnetic core 3 of readily saturable material, for example, ferrite. Next to the lower end of the vertically arranged core 3, which projects from the winding 1, a substantially cylindrical, diametrically-magnetized permanent magnet 5 engages the core, preferably as closely as possible. The axis of the cylindrical magnet 5 is parallel to that of the rod 3' and the magnet is supported to rotate about the first-mentioned axis in the housing or frame of the device, which is not shown for the sake of clarity.

The lower end of the core 3, which projects from the winding 1, is partly surrounded by a substantially U- shaped permanent magnet 7. One pole of magnet 7, that is to say the north pole, lies on the inner side of the U and the other pole, that is to say the south pole, lies on the outer side of the U. The open side of the U is adjacent the magnet 5 and this therefore lies within the sector of the space around the end of the core 3 which lies outside the magnet 7.

FIGURES 2 and 3 show the relative positions of the magnets and the end of the core in horizontal section in a plane just below the winding 1. FIGURE 2 shows the situation in which the north pole of the magnet 5 is adjacent to the core 3 and to the north pole of the magnet 7. The two north poles intensify each other and the lines of magnetic force (shown in broken lines) are closed (see also FIGURE 1) through the core 3 and the ambient air. The core 3 is then magnetically saturated at least to a considerable degree. However, in the position shown in FIG. 3, in which the south pole of magnet 5 is adjacent to the core, the lines of force pass through the said lower end of the core 3 only in the transverse direction. In this perspective view of one embodiment portion of the core is continuously adjustable by rotation of the magnet 5.

FIGURES 2 and 3 show that the U-shaped magnet 7 surrounds the rod 3, preferably at least approximately cross-sectional area. However, the magnet 7 may embrace the rod 3 over a considerably smaller portion than shown, for example, over only A to part of its periphery, but the intensification of the magnetisation by means of the magnet 7 is then considerably smaller.

possible to mount a magnet of the described able simultaneously.

What is claimed is:

1. A variable inductor comprising a ferromagnetic core of the core projects beyond the coil winding in a direction parallel to the axis of rotation of said magnet, said magnet engaging said one end of the core, a U-shaped magnet positioned to partially surround said core end U faces said cylindrical magnet, said U-shaped magnet being magnetized transversely to the axis of the core.

3. An inductor as described in claim 2 wherein said U-shaped magnet is arranged to surround said core end over at least approximately one-half of its periphery.

4. A coil system adapted for use as a linearity corrector for a television receiver comprising, a saturable ferromagnetic core, a winding disposed on said core so that a portion of the core projects beyond the winding, a cylindrical diametrically magnetized magnet mounted for rotation about its longitudinal axis, said magnet being positioned adjacent said projecting core portion with said axis arranged parallel to the core axis so that the direction of magnetization of the magnet is in planes transverse to the core axis, a U-shaped magnet positioned to partially surround said projecting core portion so that the open side of the U confronts said cylindrical magnet, said -shaped magnet being magnetized so that the poles of one polarity and of the opposite polarity lie along the inner surface thereof and along the outer surface thereof, respectively.

5. A coil system as described in claim 4 wherein said core comprises a rod-shaped member having its axis parallel to the axis of the cylindrical magnet whereby the major portion of the magnetic lines of force of said magnets are directed along the core axis when said cylindrical magnet is adjusted to the position in which like poles of the cylindrical and U-shaped magnets are adjacent the core and whereby the major portion of said lines of force pass transversely through the projecting core portion when said cylindrical magnet is adjusted to the position in which unlike poles of the cylindrical and U-shaped magnets are adjacent the core.

6. A variable inductor comprising a saturable ferromagnetic core, a Winding disposed on said core so that a portion of the core projects beyond the winding, a cylindrical diametrically magnetized magnet positioned adjacent said projecting core portion so that its direction of magnetization is transverse to the core axis, said magnet being rotatively supported about its axis for movement of either of the poles thereof selectively into contiguous relation to said core, a second magnet magnetized transversely to the core axis and diametrically disposed on the opposite side of the projecting core portion so as to partially surround same, said second magnet being maintained in fixed contiguous relation to said projecting core portion.

References Cited UNITED STATES PATENTS 2,915,637 12/1959 McAdam 336-110 X 3,005,157 12/1961 Spinrad 336110 X 3,020,503 2/1962 Reijnst 336-110 3,151,305 9/1964 Simpson 336-110 OTHER REFERENCES Schmitt, German application No. 1,164,578, published Mar. 5, 1964.

LEWIS H. MYERS, Primary Examiner.

5 T. J. KOZMA, Assistant Examiner. 

1. A VARIABLE INDUCTOR COMPRISING A FERROMAGNETIC CORE HAVING A SATURABLE SECTION, A COIL DISPOSED ON SAID CORE SO THAT A PORTION OF THE CORE IS EXPOSED AT ONE END, A CYLINDRICAL DIAMETRICALLY MAGNETIZED MAGNET MOUNTED FOR ROTATION ABOUT A GIVEN AXIS, SAID MAGNET ENGAGING SAID END OF THE CORE SO THAT SAID AXIS OF ROTATION IS PARALLEL TO SAID CORE END, AND A U-SHAPED PERMANENT MAGNET MAGNETIZED SO THAT THE POLES OF ONE POLARITY LIE ALONG THE INNER SURFACE THEREOF AND THE POLES OF OPPOSITE POLARITY LIE ALONG THE OUTER SURFACE THEREOF, SAID U-SHAPED MAGNET BEING DISPOSED SO AS TO PARTIALLY SURROUND SAID CORE END WITH THE OPEN SIDE OF THE U ADJACENT BUT SPACED APART FROM SAID CYLINDRICAL MAGNET. 